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GHSA-GHFH-7XFW-63JP

Vulnerability from github – Published: 2026-08-15 06:32 – Updated: 2026-08-17 06:33

Details

In the Linux kernel, the following vulnerability has been resolved:

ipv4: igmp: Fix potential UAF in igmp_gq_start_timer()

A race condition exists between device teardown (inetdev_destroy) and incoming IGMP query processing (igmp_rcv), leading to a Use-After-Free in the IGMP timer callback.

During device destruction, inetdev_destroy() drops the primary reference to in_device, which can drop its refcount to 0. The actual freeing of in_device memory is deferred via RCU (using call_rcu()).

Concurrently, igmp_rcv() runs under RCU read lock and obtains the in_device pointer. Because the memory is RCU-protected, CPU-0 can safely dereference in_device even if its refcount has hit 0.

However, if CPU-0 calls igmp_gq_start_timer() and re-arms the timer, it attempts to acquire a reference using in_dev_hold(). This increments the refcount from 0 to 1, triggering a "refcount_t: addition on 0" warning. Since the in_device memory is still scheduled to be freed after the RCU grace period (as the free callback does not check the refcount again), the device is freed while the timer is still armed. When the timer expires, it accesses the freed memory, causing a kernel panic.

Fix this by using refcount_inc_not_zero() (via a new helper in_dev_hold_safe()) to prevent acquiring a reference if the device is already being destroyed. If the refcount is 0, we do not arm the timer.

A similar issue in IPv6 MLD is fixed in a subsequent patch.

Severity

9.8 (Critical)


                  
                    CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H

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{
  "affected": [],
  "aliases": [
    "CVE-2026-72323"
  ],
  "database_specific": {
    "cwe_ids": [],
    "github_reviewed": false,
    "github_reviewed_at": null,
    "nvd_published_at": "2026-08-15T06:22:05Z",
    "severity": "CRITICAL"
  },
  "details": "In the Linux kernel, the following vulnerability has been resolved:\n\nipv4: igmp: Fix potential UAF in igmp_gq_start_timer()\n\nA race condition exists between device teardown (inetdev_destroy) and\nincoming IGMP query processing (igmp_rcv), leading to a Use-After-Free\nin the IGMP timer callback.\n\nDuring device destruction, inetdev_destroy() drops the primary reference\nto in_device, which can drop its refcount to 0. The actual freeing of\nin_device memory is deferred via RCU (using call_rcu()).\n\nConcurrently, igmp_rcv() runs under RCU read lock and obtains the\nin_device pointer. Because the memory is RCU-protected, CPU-0 can safely\ndereference in_device even if its refcount has hit 0.\n\nHowever, if CPU-0 calls igmp_gq_start_timer() and re-arms the timer, it\nattempts to acquire a reference using in_dev_hold(). This increments the\nrefcount from 0 to 1, triggering a \"refcount_t: addition on 0\" warning.\nSince the in_device memory is still scheduled to be freed after the RCU\ngrace period (as the free callback does not check the refcount again),\nthe device is freed while the timer is still armed. When the timer\nexpires, it accesses the freed memory, causing a kernel panic.\n\nFix this by using refcount_inc_not_zero() (via a new helper\nin_dev_hold_safe()) to prevent acquiring a reference if the device is\nalready being destroyed. If the refcount is 0, we do not arm the timer.\n\nA similar issue in IPv6 MLD is fixed in a subsequent patch.",
  "id": "GHSA-ghfh-7xfw-63jp",
  "modified": "2026-08-17T06:33:23Z",
  "published": "2026-08-15T06:32:20Z",
  "references": [
    {
      "type": "ADVISORY",
      "url": "https://nvd.nist.gov/vuln/detail/CVE-2026-72323"
    },
    {
      "type": "WEB",
      "url": "https://git.kernel.org/stable/c/165258303357e54b75fc19b341ae2a2b7c9e3910"
    },
    {
      "type": "WEB",
      "url": "https://git.kernel.org/stable/c/40a1e998cb266ed4cb529a0bb4fee2b0ba732702"
    },
    {
      "type": "WEB",
      "url": "https://git.kernel.org/stable/c/75e984fe0cb9e7fbde0c8ee838c61ce8573d3ea3"
    },
    {
      "type": "WEB",
      "url": "https://git.kernel.org/stable/c/7b19c0f81ed1fdaec6bc522569be367199a9edf3"
    },
    {
      "type": "WEB",
      "url": "https://git.kernel.org/stable/c/8d4394ffa40508e0de72f464af351f6ca6a6cdc3"
    }
  ],
  "schema_version": "1.4.0",
  "severity": [
    {
      "score": "CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H",
      "type": "CVSS_V3"
    }
  ]
}

CVE-2026-72323 (GCVE-0-2026-72323)

Vulnerability from cvelistv5 – Published: 2026-08-15 05:55 – Updated: 2026-08-17 05:42

Title

ipv4: igmp: Fix potential UAF in igmp_gq_start_timer()

Summary

In the Linux kernel, the following vulnerability has been resolved: ipv4: igmp: Fix potential UAF in igmp_gq_start_timer() A race condition exists between device teardown (inetdev_destroy) and incoming IGMP query processing (igmp_rcv), leading to a Use-After-Free in the IGMP timer callback. During device destruction, inetdev_destroy() drops the primary reference to in_device, which can drop its refcount to 0. The actual freeing of in_device memory is deferred via RCU (using call_rcu()). Concurrently, igmp_rcv() runs under RCU read lock and obtains the in_device pointer. Because the memory is RCU-protected, CPU-0 can safely dereference in_device even if its refcount has hit 0. However, if CPU-0 calls igmp_gq_start_timer() and re-arms the timer, it attempts to acquire a reference using in_dev_hold(). This increments the refcount from 0 to 1, triggering a "refcount_t: addition on 0" warning. Since the in_device memory is still scheduled to be freed after the RCU grace period (as the free callback does not check the refcount again), the device is freed while the timer is still armed. When the timer expires, it accesses the freed memory, causing a kernel panic. Fix this by using refcount_inc_not_zero() (via a new helper in_dev_hold_safe()) to prevent acquiring a reference if the device is already being destroyed. If the refcount is 0, we do not arm the timer. A similar issue in IPv6 MLD is fixed in a subsequent patch.

Severity

9.8 (Critical)


                        
                          CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H

Assigner

Linux mitre root

References

5 references

URL	Tags
https://git.kernel.org/stable/c/40a1e998cb266ed4c…
https://git.kernel.org/stable/c/165258303357e54b7…
https://git.kernel.org/stable/c/75e984fe0cb9e7fbd…
https://git.kernel.org/stable/c/8d4394ffa40508e0d…
https://git.kernel.org/stable/c/7b19c0f81ed1fdaec…

Impacted products

2 products

Vendor	Product	Version
Linux	Linux	Affected: 1da177e4c3f41524e886b7f1b8a0c1fc7321cac2 , < 40a1e998cb266ed4cb529a0bb4fee2b0ba732702 (git) Affected: 1da177e4c3f41524e886b7f1b8a0c1fc7321cac2 , < 165258303357e54b75fc19b341ae2a2b7c9e3910 (git) Affected: 1da177e4c3f41524e886b7f1b8a0c1fc7321cac2 , < 75e984fe0cb9e7fbde0c8ee838c61ce8573d3ea3 (git) Affected: 1da177e4c3f41524e886b7f1b8a0c1fc7321cac2 , < 8d4394ffa40508e0de72f464af351f6ca6a6cdc3 (git) Affected: 1da177e4c3f41524e886b7f1b8a0c1fc7321cac2 , < 7b19c0f81ed1fdaec6bc522569be367199a9edf3 (git)
Linux	Linux	Affected: 2.6.12 Unaffected: 0 , < 2.6.12 (semver) Unaffected: 6.6.145 , ≤ 6.6.* (semver) Unaffected: 6.12.97 , ≤ 6.12.* (semver) Unaffected: 6.18.40 , ≤ 6.18.* (semver) Unaffected: 7.1.5 , ≤ 7.1.* (semver) Unaffected: 7.2 , ≤ * (original_commit_for_fix)

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{
  "containers": {
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          "defaultStatus": "unaffected",
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          "programFiles": [
            "include/linux/inetdevice.h",
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              "versionType": "git"
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          "vendor": "Linux",
          "versions": [
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              "status": "unaffected",
              "version": "6.12.97",
              "versionType": "semver"
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            {
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              "status": "unaffected",
              "version": "6.18.40",
              "versionType": "semver"
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            {
              "lessThanOrEqual": "7.1.*",
              "status": "unaffected",
              "version": "7.1.5",
              "versionType": "semver"
            },
            {
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              "status": "unaffected",
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              "versionType": "original_commit_for_fix"
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      ],
      "cpeApplicability": [
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          "value": "In the Linux kernel, the following vulnerability has been resolved:\n\nipv4: igmp: Fix potential UAF in igmp_gq_start_timer()\n\nA race condition exists between device teardown (inetdev_destroy) and\nincoming IGMP query processing (igmp_rcv), leading to a Use-After-Free\nin the IGMP timer callback.\n\nDuring device destruction, inetdev_destroy() drops the primary reference\nto in_device, which can drop its refcount to 0. The actual freeing of\nin_device memory is deferred via RCU (using call_rcu()).\n\nConcurrently, igmp_rcv() runs under RCU read lock and obtains the\nin_device pointer. Because the memory is RCU-protected, CPU-0 can safely\ndereference in_device even if its refcount has hit 0.\n\nHowever, if CPU-0 calls igmp_gq_start_timer() and re-arms the timer, it\nattempts to acquire a reference using in_dev_hold(). This increments the\nrefcount from 0 to 1, triggering a \"refcount_t: addition on 0\" warning.\nSince the in_device memory is still scheduled to be freed after the RCU\ngrace period (as the free callback does not check the refcount again),\nthe device is freed while the timer is still armed. When the timer\nexpires, it accesses the freed memory, causing a kernel panic.\n\nFix this by using refcount_inc_not_zero() (via a new helper\nin_dev_hold_safe()) to prevent acquiring a reference if the device is\nalready being destroyed. If the refcount is 0, we do not arm the timer.\n\nA similar issue in IPv6 MLD is fixed in a subsequent patch."
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            {
              "lang": "en",
              "value": "AV:N - The bug is reached from igmp_rcv(), registered as the IPPROTO_IGMP handler and invoked via ip_rcv \u2192 ip_local_deliver \u2192 ip_protocol_deliver_rcu() on received IPv4 packets; per kernel guidance, net/ stack flaws triggered by inbound packets are scored Network even when practical reachability is typically same-subnet.\nAC:L - An attacker controls both race sides: flooding IGMP general membership queries while concurrently deleting/tearing down the target netdev (e.g., veth in a user/net namespace, container CNI teardown, or parallel RTNETLINK unregister), and can retry until the timer is re-armed after ip_mc_down() during inetdev_destroy().\nPR:N - IGMP query processing has no authentication or capability checks on the receive path; any host that can deliver IPPROTO_IGMP packets to the interface can trigger igmp_heard_query() \u2192 igmp_gq_start_timer(), and concurrent interface destruction is normal system/orchestrator activity rather than attacker privilege on the victim.\nUI:N - Exploitation requires only attacker-sent IGMP packets timed against interface teardown; no victim must open files, click links, mount filesystems, or take any deliberate action beyond routine network interface lifecycle events.\nS:U - The use-after-free corrupts kernel heap memory within the same host kernel security authority; it is a standard in-kernel memory corruption issue, not a VM escape, IOMMU bypass, or other cross-boundary scope change.\nC:H - This is a use-after-free of struct in_device: igmp_gq_timer_expire() dereferences freed memory and calls igmpv3_send_report(), enabling disclosure of reallocated slab contents and arbitrary kernel memory read primitives via heap grooming.\nI:H - The UAF arms mr_gq_timer on a freed in_device and the expiry handler writes through dangling pointers (mr_gq_running, igmpv3_send_report paths), providing attacker-influenced heap corruption that can be developed into arbitrary kernel write and privilege escalation.\nA:H - The fix commit states the timer callback accesses freed in_device memory and causes kernel panic; UAF on a timer-armed netdev structure is a reliable oops/panic and repeatable DoS, and can be retriggered by continued IGMP query flooding during interface churn."
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        "dateUpdated": "2026-08-17T05:42:48.993Z",
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          "url": "https://git.kernel.org/stable/c/8d4394ffa40508e0de72f464af351f6ca6a6cdc3"
        },
        {
          "url": "https://git.kernel.org/stable/c/7b19c0f81ed1fdaec6bc522569be367199a9edf3"
        }
      ],
      "title": "ipv4: igmp: Fix potential UAF in igmp_gq_start_timer()",
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  "cveMetadata": {
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    "assignerShortName": "Linux",
    "cveId": "CVE-2026-72323",
    "datePublished": "2026-08-15T05:55:34.828Z",
    "dateReserved": "2026-08-09T03:40:39.919Z",
    "dateUpdated": "2026-08-17T05:42:48.993Z",
    "state": "PUBLISHED"
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  "dataType": "CVE_RECORD",
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}

Sightings

Author	Source	Type	Date	Other

Nomenclature

Seen: The vulnerability was mentioned, discussed, or observed by the user.
Confirmed: The vulnerability has been validated from an analyst's perspective.
Published Proof of Concept: A public proof of concept is available for this vulnerability.
Exploited: The vulnerability was observed as exploited by the user who reported the sighting.
Patched: The vulnerability was observed as successfully patched by the user who reported the sighting.
Not exploited: The vulnerability was not observed as exploited by the user who reported the sighting.
Not confirmed: The user expressed doubt about the validity of the vulnerability.
Not patched: The vulnerability was not observed as successfully patched by the user who reported the sighting.

Detection rules are retrieved from Rulezet.

The MITRE ATT&CK techniques below are AI-generated suggestions, inferred from the description of the vulnerability by the CIRCL/vulnerability-attack-technique-classification-roberta-base model, served locally by ML-Gateway. They have not been verified by an analyst and are provided for guidance only.
The approach is described in our paper Mapping CVEs to MITRE ATT&CK Techniques: A Curated Gold-Set Classifier and the Limits of LLM-Assisted Label Expansion.

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GHSA-GHFH-7XFW-63JP

CVE-2026-72323 (GCVE-0-2026-72323)

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